Electrodeposited copper foil is used in a variety of products. For example, it is an indispensable part of printed circuit boards. Double-sided glossy copper foil is coated with an electrode active material and used as the negative electrode plate of a lithium ion secondary battery. Many electronic products therefore rely, at least in part, on electrodeposited copper foil.
A typical device for manufacturing an electrodeposited copper foil comprises a metal cathode drum and an insoluble dimensionally stable anode (DSA), the metal cathode drum being rotatable and having a mirror polished surface. The insoluble metal anode is arranged at approximately the lower half of the metal cathode drum and surrounds the metal cathode drum. An electrodeposited copper foil is continuously manufactured with the device by flowing a copper electrolytic solution between the cathode drum and the anode, applying direct current between these to allow copper to be electrodeposited on the cathode drum, and detaching an electrodeposited copper foil from the cathode drum when a predetermined thickness is obtained.
The variation of thickness of the electrodeposited copper foil is determined by a number of variable process parameters. The production efficiency of electrodeposited copper foil, especially ultra-thin copper foil, is reduced by a tendency for the raw foil to tear during the course of the processing. This problem is especially severe when variations of thickness occur in the copper foil. The thin regions of the foil are weaker than the thick regions. Furthermore, variations in thickness lead to other problems such as curling of the copper foil and formation of wrinkles (sometimes referred to as elongation wrinkles). Moreover, use of copper foil having large variations in thickness in electrical devices such as batteries and circuit boards, can reduce the life-span of these devices due to deterioration or failure.